In My account --> Personal Details --> Profile --> Locale Details I set my language as English and country as United States.
When I use my PC at home, with the English version of Windows 7, I don't have any problems.
When I use a computer at work, with Japanese Windows, in some areas of zoho.com the interface does indeed display in English, as specified in locale details. In other parts, such as Zoho Creator, the interface is still mostly shown in Japanese.
What the hell is up with this? Makes my productivity incredibly slow, as I'm not so good reading Japanese! I find zoho.com to be slightly amateur at times, I'm sad to say.